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<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
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  <body>
    <script>
      let x = 200;
      let y = 400;
      function f1(a, b) {
        // let a = x; 复制了x值
        // let b = y; 复制了y值
        // 形参
        a = 10;
        b = 20;
        console.log("a:", a, "b:", b);
      }

      f1(x, y); // 实参
      console.log("x:", x, "y:", y);
    </script>
  </body>
</html>
